Telephony provider permission denied

Support Help
1

Hi

when i tried test call I have:

telephony provider permission denied

What is the problem?

2

The telephony_provider_permission_denied error means that SIP trunk authentication failed(1). This represents cases where the SIP trunk authentication failed(1).

Here’s how to troubleshoot:

Check your call detailed log - it contains the disconnection reason, SIP error code, and error message(1).

If using custom telephony:

  • Double check your configuration and ensure you imported the right information(1)
  • If the configuration is incorrect, delete the imported number and re-import(1)
  • Check with your telephony provider to see what error is on their side(1)

If using numbers purchased from Retell:

  • Make sure the destination number can accept the call(1)
  • Currently, numbers purchased from Retell can only make calls to US numbers(1)

Common issues to verify:

  • Ensure your Termination SIP URI has no spaces(2)
  • Verify your username and credentials are correct (the username is different from the friendly name)(2)
  • If using Twilio, check that you’ve configured authentication correctly via IP whitelisting or username/password credentials(2)
3

call_fbf6d77b8b3ffc56691eb22ace2

My credential is I think correct.

4

I’ve seen this before it usually just means Retell doesn’t have permission to use the telephony provider yet. Most times it’s something simple like the provider (Twilio, etc.) not being fully connected, the API keys being wrong, the number not active, or the account not funded.

I’d check that outbound calling is enabled, the number is verified, and the region matches where you’re testing the call. Once those are sorted, the test call normally goes through.

5

Your instincts are correct. When outbound calls fail with telephony provider permission errors, the most common issues are with the SIP trunk configuration in your telephony provider.

For Twilio specifically, check your Termination SIP URI for any spaces and remove them(1). You should also use a localized termination URI near your region(1). Verify your username and credentials are correct—note that the username is different from the friendly name shown in the credential list(1).

If you’re using IP-based authentication instead of credentials, you need to whitelist Retell’s IP addresses. Since Retell’s SIP server doesn’t have a static IP, you need to whitelist all IP addresses in these ranges: 18.98.16.120/30 (all regions), 143.223.88.0/21 (certain United States traffic), and 161.115.160.0/19 (certain United States traffic)(2).

For international calling, search “geo” to find the “Voice Geographic Permissions” setting in Twilio(1). Choose “Elastic Sip Trunking” in the selector and select the countries you want to dial(1).

After configuring your SIP trunk, you need to import the number into Retell using the termination SIP URI you set up(1). If you configured authentication via credentials, provide the username and password during import(1)(3).

6

Hello @Sevana

Can you share the call id?